With the ever-growing threat of bioterrorist attacks, the development of technology to aid in the quick identification and possible counteraction of such attacks is merited. Bioterrorist attacks reach far beyond anthrax powder or food contamination. Aerosol technology aids in the infusion of biochemical threats into the air. In the past, it was more feasible to rely on laboratory settings for the examination of potential biowarfare agents, but at present people are confronted with more widespread threats and potential hoaxes making on-site testing essential. This is the type of threat technology to which an Optical Particle Counter (OPC) may be applied.
An OPC acts as an on-site, inexpensive, and widely disseminating detector for the carriers of these biochemical threat agents, as opposed to trying to detect the actual threat agents, which is a slower and more costly process. The OPC is an instrument based on the principle of light scattering from particles typically used to measure particles above 0.05 micrometers in diameter. Such instruments have been used by environmental engineers to measure size distribution of particulate pollutants in the ambient atmosphere, in exhausts of industrial devices such as smelters, coal combustors, and automobiles; also for measuring efficiencies of particle control equipment and also to calibrate other instruments. OPCs are also used by industrial hygienists to sample particles in occupational environments. Pharmacists use them to size and classify their powdered drugs.
Analysis of the size spectrum thereby reveals the presence of different sources of aerosol and alerts one to the introduction and presence of foreign, extraneous, sources to the average background. Flowing particles can be analyzed using light scattering techniques, in real time, in order to measure each particle's size. This aerosol spectrometry gives data on both the number and size of particles suspended in an air stream. Research has shown that the mean particle size based on the number distribution is substantially less than one micrometer. Thus, generation of particles larger than one micrometer, which is common for most biological aerosol generation systems, is easily detected against very low background number concentrations in any one micrometer-wide size range (at concentrations above 0.1 particles per cubic meter).
Examples of background art in this technical area include U.S. Pat. No. 2,732,753 to O'Konski, which determines the viability of particles using a dye with detectable fluorescent properties; and U.S. Pat. No. 6,787,302 to Fleming, which detects and quantifies viable cell samples using fluorescent dyes.
Yet another example of a background art method for particulate counting and a biomass indicator is the AMEBA Biosensor, which monitors physiological response data from microorganisms exposed to aerosolized samples. In addition, a Digital Smell/Electric Nose comprising: an array of gas sensors with different selectivity patterns; a signal-collecting unit; and pattern recognition software, can also be used as a diagnostic system based on detecting volatile gases given off as metabolites by microorganisms. As an example, these devices are commercially available for the detection of the microorganisms causing bacterial pharyngitis.
Although, as discussed above, there are a number of biosensors on the market today, the following technical obstacles have limited them with respect to providing a quintessential biosensor. These technical obstacles include, but are not limited to: (1) stability of the bio-receptor; (2) assay sensitivity; (3) variation in sensitivity; Specificity of analytic detection; Noise interference; Miniaturization; viable cells count; and Time for assay protocol. In addition to this, the paradigm for threat detection used by many devices does not adequately account for the nature of aerosol generation. Any technique specifically designed for the purpose of aerosol generation will yield a different, usually narrower, particle size spectrum than the “normal” background size spectrum. Therefore, there is a need in the art for a system and method that detects a specific size spectrum and will alert the user to the presence of extraneous, possibly threatening agents.